1. Field of the Invention
The present invention relates to a cylindrical vibration damping bushing, and more particularly to a simply-structured vibration damping bushing which is preferably used in a coupling portion of a vehicle part such as a suspension arm.
2. Description of the Prior Art
Conventional cylindrical vibration damping bushing are provided with a vibration damping rubber body between coaxially disposed inner and outer cylinders, and are frequently used in portions of a vehicle which require vibration isolation.
In the cylindrical vibration damping bushing used in the coupling portion of the suspension arm, the inner cylinder and the outer cylinder are ordinarly rotatable relative to each other.
Recently, in order to improve the ride of a vehicle, vibration damping bushing have been developed which enable the twistable rocking of the suspension arm without any resistance. Several examples of such vibration damping bushings are disclosed in Japanese unexamined utility model publications Nos. Sho 61-49143, 62-110617, 62-110619 and 62-110644, and Japanese examined utility model publication No. Sho 63-44572. These vibration damping bushings are characterized in that an axially central portion of the inner cylinder has a spherical expanded portion, and that a vibration damping rubber body and an outer cylinder are disposed in that order around the spherical expanded portion through a resin member.
However, the above-described conventional vibration damping bushings have a relatively complex construction. They require race metal fittings for retaining the resin member, and seal members for retaining lubricant between the expanded portion and the resin member. This result in difficult assembly and maintenance of these members and accordingly the production costs are increased.